Patent GB-738284-A (GB)
Title: Improvements in inert gas shielded electric arc welding
Inventor: MULLER ALBERT
IPC: B23K35/22
Filed: 1952-07-28
Abstract: 738,284. Welding by fusion. AIR REDUCTION CO., Inc. July 28, 1952, No. 19009/52. Class 83 (4). In inert gas shielded arc welding with a consumable electrode, a material which is electro-positive relative to the metal of the cathode and effective to increase the thermionic electron emission thereof is introduced into the welding zone to reduce the heat produced at the cathode. The material may be in the surface of the electrode, embodied in the electrode as an alloying or mixing element, entrained in the shielding gas stream, applied directly on the workpiece or added on the surface of a filler wire. The material co-operates with the arc cathode to form a composite cathode surface having a higher thermionic emission than the cathode base metal alone. The material is preferably a metal with an ionization potential lower than that of any of the other constituents of the arc atmosphere. The material may be selected from the alkali metals lithium, sodium, potassium, rubidium, cerium and francium; the alkaline earth metals calcium, barium, strontium and radium; lanthanum and lanthanum series rare earth metals cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutesium; actinium and the actinium series rare earth metals thorium, protactinium, uranium, neptunium, plutonium, americium, curium; scandium and yttrium. Compounds of these elements which dissociate in the ore to liberate the elements may be used, e.g. the oxides, carbonates, borates, phosphates, nitrates, silicates or halides. Preferred materials are cesium nitrate, rubidium carbonate, cesium rubidium chloride, barium oxide or carbonate, barium strontium mixtures in the form of oxides or carbonates, lanthanum and lanthanum series metals in oxide forms, thorium oxide and potassium carbonate. For common structural metal welding an element is preferably selected from potassium, rubidium, cesium, strontium, barium, lanthanum or lanthanum rare earth mixtures, cerium, thorium and uranium. The use of the added materials concentrates the arc cathode spot, improves transfer of metal from the electrode and stabilizes the arc. The workpiece and electrode may consist of aluminium, aluminium alloys, iron, copper, copper alloys, nickel, nickel alloys, magnesium and magnesium alloys. In an embodiment a mild steel wire is knurled in rolls and a paste of rubidium carbonate and alcohol is brushed on the surface and some is trapped therein when the wire is passed through smoothing rolls. The wire is dried and fed from a reel 23, Fig. 1, through a conduit 26 to a gun 27. Argon is supplied through the conduit 26 to the gun 27 to be discharged therefrom as an annular non-turbulent stream. D.C. straight polarity (negative electrode) is used. Rubidium oxide or barium oxide may be used in place of rubidium carbonate, the barium oxide with D.C. reverse polarity (positive electrode). An aluminium alloy wire with cesium nitrate in the surface may be used in the apparatus of Fig. 1, using D.C. straight polarity. An aluminium electrode with cesium nitrate in its surface is employed with D.C. reverse polarity. Using the apparatus of Fig. 1 welds were made on a steel plate using an aluminium bronze-9 per cent Al., balance Cu.-wire with cesium rubidium chloride in the surface using D.C. straight polarity. In another embodiment an electrode made from molten mild steel to which misch metal is added-52 per cent cerium, 33 per cent lanthanum, 1.5 per cent iron balance rare earthmetals-is employed with argon using D.C. straight polarity. In another embodiment an untreated metal steel electrode 90, Fig. 16, is fed from a reel 91 through a conduit 93 to a gun 94. Argon is supplied to the gun 94 from a cylinder 110 to flow non-turbulently from a water-cooled nozzle. Steel filler wire 119 with barium oxide in its surface is fed to the D.C. reverse polarity arc from a reel 120 through a conduit 122. In a further embodiment using a gun similar to that in Fig. 16, powdered barium oxide is introduced by a vibrating powder disperser into an argon shielding gas stream about a mild steel electrode. In a further embodiment a slurry of barium oxide and alcohol is applied by brush to the workpiece. Specifications 662,806, 684,011 and 687,666 are referred to.